The present invention relates to a magnetic head or magnetic disk testing apparatus(an Inspection Apparatus and inspection method of magnetic disk or magnetic head). More particularly, the present invention relates to a technique for accurately detecting the amplitude of servo (hereinafter referred to as burst data) signals to provide accurate positioning of a magnetic head.
A magnetic head or magnetic disk testing apparatus is configured to determine the quality or other aspects of a magnetic head or a magnetic disk, by locating the magnetic head above the magnetic disk, writing and reading test data through the magnetic head on a target track, and measuring the characteristics of a signal read from the target track. Heretofore, servo control has been performed for accurately positioning the magnetic head on a target track of the magnetic disk.
To achieve the above, several techniques have been proposed, such as those described in JP-A No. 141807/1995 and JP-A No. 242152/2007. The technique of JP-A No. 141807/1995 is configured to transmit an amplitude detection signal of burst data through a band-pass filter, an analog to digital conversion circuit, and a digital filter. The technique of JP-A No. 242152/2007 is configured to apply Fast Fourier Transform (FFT) to burst data with a plurality of different frequency components, for detecting the amplitude ratio of each frequency component.